/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/calls/calls.h"
#include "libc/calls/cp.internal.h"
#include "libc/calls/struct/timespec.h"
#include "libc/calls/struct/timespec.internal.h"
#include "libc/calls/syscall-sysv.internal.h"
#include "libc/cosmo.h"
#include "libc/cosmotime.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/intrin/atomic.h"
#include "libc/intrin/weaken.h"
#include "libc/limits.h"
#include "libc/runtime/syslib.internal.h"
#include "libc/sysv/consts/clock.h"
#include "libc/sysv/errfuns.h"
#include "libc/thread/semaphore.h"
#include "libc/thread/thread.h"

static void sem_timedwait_cleanup(void *arg) {
  sem_t *sem = arg;
  unassert(atomic_fetch_add(&sem->sem_waiters, -1) > 0);
}

/**
 * Locks semaphore w/ deadline.
 *
 * @param abstime is absolute deadline or null to wait forever
 * @return 0 on success, or -1 w/ errno
 * @raise ECANCELED if calling thread was cancelled in masked mode
 * @raise EINTR if signal was delivered instead
 * @raise EDEADLK if deadlock was detected
 * @raise ETIMEDOUT if deadline expired
 * @raise EINVAL if `sem` is invalid
 * @cancelationpoint
 */
int sem_timedwait(sem_t *sem, const struct timespec *abstime) {
  int v, rc, e = errno;

  rc = sem_trywait(sem);
  if (!rc) {
    return rc;
  } else if (errno == EAGAIN) {
    errno = e;
  } else {
    return rc;
  }

  BEGIN_CANCELATION_POINT;
  unassert(atomic_fetch_add(&sem->sem_waiters, +1) >= 0);
  pthread_cleanup_push(sem_timedwait_cleanup, sem);

  do {
    if (!(v = atomic_load_explicit(&sem->sem_value, memory_order_relaxed))) {
      rc = cosmo_futex_wait(&sem->sem_value, v, sem->sem_pshared,
                            CLOCK_REALTIME, abstime);
      if (rc == -EINTR || rc == -ECANCELED) {
        errno = -rc;
        rc = -1;
      } else if (rc == -EAGAIN || rc == -EWOULDBLOCK) {
        rc = 0;
      } else if (rc == -ETIMEDOUT) {
        npassert(abstime);
        if (timespec_cmp(*abstime, timespec_real()) <= 0) {
          rc = etimedout();
        } else {
          rc = 0;
        }
      } else {
        npassert(!rc);
        rc = 0;
      }
    } else if (v > 0) {
      rc = 0;
    } else {
      unassert(v > INT_MIN);
      rc = einval();
    }
  } while (!rc &&
           (!v || !atomic_compare_exchange_weak(&sem->sem_value, &v, v - 1)));

  pthread_cleanup_pop(1);
  END_CANCELATION_POINT;

  return rc;
}
